Knowra Population II star Population II star A star formed from gas enriched by earlier generations of stars, typically with low abundances of elements heavier than helium. Population II stars are generally old and often found in the Milky Way’s halo and globular clusters.
Stellar metallicity : The abundance of elements heavier than helium in a star, often expressed relative to the Sun. Low metallicity is the defining chemical signature of most Population II stars.
Big Bang nucleosynthesis : The production of light atomic nuclei during the first minutes of the universe. It left primordial gas with very few elements heavier than helium before Population II formation.
Galactic halo : The extended, roughly spherical region surrounding a galaxy’s visible disk, containing stars, gas, and dark matter. Many of the Milky Way’s oldest Population II stars occupy this region.
Galactic archaeology : The study of a galaxy’s formation and evolution using the present-day properties of its stars. Population II stars act as surviving records of the Milky Way’s early assembly.
Stellar population : A grouping of stars classified by shared properties such as age, chemical composition, and location. Population II is one of the traditional categories used to classify stars.
First stars : The earliest stars to form from primordial matter in the young universe. Their deaths began enriching gas from which later, metal-poor stars could form.
Globular cluster : A dense, gravitationally bound cluster containing hundreds of thousands to millions of stars. Many globular clusters contain old, metal-poor stars traditionally classified as Population II.
Stellar halo stream : An elongated structure of stars left behind when a smaller stellar system is disrupted by a galaxy. Metal-poor Population II stars in streams can trace the accretion of ancient satellites.
Population I star : A relatively young, metal-rich star, commonly found in a galaxy’s disk. Its younger age and greater metal abundance contrast with the usual Population II pattern.
Supernova nucleosynthesis : The creation and dispersal of chemical elements during stellar explosions. Supernova ejecta enriched the gas that formed many Population II stars.
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